Entrainment separator for wiped thin film processor



Feb. 15, 1966 BELCHER 3,234,993

ENTRAINMENT SEPARATOR FOR WIPED THIN FILM PROCESSOR Filed Oct. 5, 1961INVENTOR, Harold H. Belcher ATTORNEYS United States Patent 3,234,993ENTRAINMENT SEPARATOR FOR WIPED THIN FILM PROCESSOR Harold H. Belcher,Orange, Mass., assignor, by mesne assignments, to Chemetron Corporation,Chicago, Ill.,

a corporation of Delaware Filed Oct. 5, 12961, Ser. No. 143,158 Claims.(Cl. 159-6) This invention relates to a thin film processor and moreparticularly to an improved entrainment separator for such a processorwhich will prevent the undesired carryover of fine droplets of liquid inthe discharge vapor stream.

The apparatus of the present invention is of the general type known as athin film evaporator. Equipment of this type is commonly used forprocesses of evaporation or distillation, but may be used for other heator mass transfer processes. In such processes, a liquid feed material isintroduced at the top of an externally heated hollow cylinder, flowsdown the inside wall of the cylinder by gravity as a thin film, and isagitated or fanned by a concentric rotor. Vapors generated rise to thetop of the unit, usually through a mist or entrainment separator, anddischarge from a vapor discharge pipe.

Separators commonly used at present are of three general types. They aregravity settling, packed bed and centrifugal throw-out. All of thesetypes have certain disadvantages.

The gravity settling type requires large chambers wherein vaporvelocities become low enough to permit gravity to settle out the heavierdroplets of entrained liquid. These large chambers are usually so largethat they cannot readily be accommodated in the processor structure butmust be built as separate units. Costs are high and piping inlets andoutlets losses make the pressure drop undesirably high.

Packed bed systems filter the vapors through a compact mass of fibers,Wire or ceramic shapes. These beds may be made quite compact butpressure drops are undesirably high and tend to become even higher asthe bed clogs up with separated liquid.

Centrifugal throw-out separators exist in many forms. In the commonform, the rising column of vapor swirling around at the rotor speed isforced to move outward toward an expanded diameter section and then isforced inward again. The entrained droplets, swirling with the vaporcolumn, are thrown out to the wall of the expanded diameter section bycentrifugal force. Since vapor voltime in thin film processors is oftenvery high, the flow cross-section out to the expanded section, upthrough this separator section, and back into the processor body must bequite large, resulting in separators of greatly expanded diameters andheights ranging up to 2 or 3 times the diameter of the main processorbody. This type of separator adds greatly to the cost, overall heightand overall diameter of the processor.

According to the present invention, it has been found that thesedifficulties may be overcome by using a novel centrifugal separator.This separator assembly is so constructed as to require the vapor andany droplets that might be contained therein to move against acentrifugal force before emerging from the assembly. This movementagainst the centrifugal force causes substantially all of the dropletsto be retained within the assembly with only the desired vapor beingwithdrawn.

Accordingly, the primary object of this invention is to provide a methodand apparatus for evaporating or concentrating liquids in which lossesare held at a minimum.

Another object of this invention is to provide a method and apparatus inwhich droplets are prevented from escaping the evaporating assembly.

3,234,993 Patented Feb. 15, 1966 Yet another object of the presentinvention is to obtain an improved separator which has a minimumpressure loss.

Still another object of this invention is to provide a separator withminimum space requirements of both diameter and height.

These and further objects and advantages of the invention will be moreapparent upon reference to the following description and claims, and theappended drawings, wherein:

FIGURE 1 is a broken side elevation and sectional view of a thin filmevaporator having a separator constructed in accordance with thisinvention;

FIGURE 2 is a more detailed section of the novel separator shown inFIGURE 1; and

FIGURE 3 is a horizontal sectional view in the plane 33 of FIGURE 2.

The same reference numerals denote the same parts throughout the severalviews of the drawings.

Referring particularly to FIGURE 1, the thin film type processor, showngenerally at 10, is tubularly constructed and is normally operated in avertical position. The lower section, indicated generally at 12, is theevaporator portion while the upper section, indicated generally at 14,is the separator portion of the apparatus. Material to be processedenters through an inlet pipe or fitting 16, which is generally locatedbetween the evaporator 12 and the separator 14, and flows down the innerwall of the vertical cylinder 18 under the influence of gravity. Theconcentrated liquid is withdrawn or discharged through a conicalcollector or fitting 20 which is secured to the bottom of the evaporator12 by a flange arrangement 21. The vapor produced by the evaporator isdischarged through a pipe or conduit 22 located above the separator 14.

The wall 18 of the evaporator portion is generally cylindricalthroughout substantially the entire length of the evaporator chamber.This wall may, however, be formed of other shapes such as, for example,a frusto-conical. Thus, while a cylindrical chamber is preferred, it isto be understood that the term cylindrical when applied to theevaporator 12 includes also other shapes that may be found desirable.

Surrounding the vertical cylinder wall 18 of the evaporator is a steamjacket 24 provided with suitable inlet and outlet ports (not shown)which are in turn connected to a source of steam and a drain,respectively. The flow of steam within the jacket 24 causes the wall 18to be heated to a desired temperature, thereby evaporating the materialflowing down the inner wall 18 in a manner well known in the processorart.

Located within the evaporating chamber is a concentric rotor body 26which extends throughout substantially the full length of the chamber.The rotor 26 is smaller than the evaporating chamber formed by the wall.18 and is provided With a plurality of blades or vanes 28 which extendoutward from the rotor into close proximity with wall 18. Ordinarily,these vanes or blades 28 are flat strips of metal or the like and aredesigned to pass in close proximity with the wall 18 throughout theirlongitudinal length. The clearance between the vanes 28 and the wall 18is kept as small as possible within reasonable mechanical limitationswith the blade tip preferably contacting or just clearing the film ofmaterial on the wall.

The rotor body 26 has top and bottom shafts 30 and 32, respectively,carried in suitable bearings 34 and 36, respectively. The bearing 36 maybe supported by a conventional spider support arrangement. Thesebearings may be of any suitable type which will prevent the escaping of,and will not contaminate, the material undergoing processing.

As better seen in FIGURE 2, the evaporating or processing chamber 18terminates at its top with a flange 37. The casing of the entrainmentseparator section 14 consists of a vertical cylindrical section 38 whichis slightly larger in diameter than the wall 18 of the evaporator 1-2.The section 38 is fitted at its lower end with a flange 40 which boltsto the flange 37 of the evaporator. The upper end of the section 38 isalso provided with flange 42 which bolts to a top closure plate 44 whichin turn carries at its center the upper bearing 34. The vapor outlet 22is also shown connected to the upper part of the section 38.

As can be seen in FIGURE 2, the rotor body 26 and blades 28 do notextend into the entrainment separator section but stop slightly belowthe top of cylinder 18. The shaft 30, which is of smaller diameter thanrotor body 26, extends upward through the entrainment separator sectionand carries a novel separator assembly indicated generally at 46.

This novel separator 46 consists of a hub 48, which is slidaible onshaft 30 and is secured to the shaft by set screws or other lockingdevices, a number of evenly spaced vertical plate spokes or separatorblades 50, a feed distributor cylinder 52 and a number of concentricalbaflle rings 54-60, assembled as shown. The separator blades 50 aresecured to and extend radially outward from the hub 48, as seen inFIGURE 3. The upper edges of the separator blades 50 are stepped asshown in FIGURE 2 to locate and receive the series of concentric baflierings 4-60. These rings are secured to the blades 50 by any suitablemethod such as welding.

The inside diameter of the lower ring 60 is approximately equal to theoutside diameter of the rotor body 26 and the outside diameter of theupper ring 54 is approximately equal to the outside diameter of theflared lower end of feed distributor cylinder 52. The number and exactposition of the baflle rings 54-60 may be varied but, in general, theinside diameter of each ring should be approximately equal to theoutside diameter of the next ring below it in the assembly.

The feed distributor cylinder 52, which is located around and secured tothe blades 50, has an outside diameter which is slightly less than theinside diameter of cylinder 18. The lower edge 53 of the feeddistributor cylinder 52 is flared outward as shown with the diameter ofthe lower edge of the flare being a small fraction less than the insidediameter of the cylinder .18. The cylinder 5-2 is also secured to thelarger of the concentric batfle rings 54 by any appropriate method suchas welding.

The separator assembly 46 is now positioned on shaft 30 by sliding thehub 48 until the lower edge 53 of the feed distributor cylinder 52 iswithin cylinder 18 just above the upper end of the blades 28. The hub isthen securely connected to the shaft 30 by appropriate locking deviceswhich are not shown.

A feed compartment ring 62, which is located with its lower surfaceapproximately in line with the upper surface of the bafiie ring 54, iswelded to the separator section cylinder 38. The inlet or feed pipe 16is also welded to the wall 38 so that it empties into the annular feedcompartment or area 64 formed by the wall 38, ring 62 and feeddistributor cylinder 52.

In operation, the shaft '30 and separator assembly 46 are startedrotating at a selected speed and the material or liquid which is to beprocessed enters the feed compartment 64 by way of feed pipe 16. As theliquid hits the wall of the compartment 64, it will begin to flow towardthe bottom of the compartment where it will run out the conical wall 39of cylinder 38 and come into contact with the outward flare portion 53of the distributor cylinder 52. This cylinder 52, which is rotating withthe rotor 26 and shaft 30, imparts a rotating velocity to the liquidfeed, forcing it down and out along the slope of the lower edge flare 53and discharging it evenly and with a slight downward velocity componenton the wall of the heated cylinder 18 of the evaporator chamber.

The liquid, as it progresses down the wall 18, is acted on by the blades28 and heated from the heat source in jacket 24. Vapors which are thusformed will rise through the unit, through the separator assembly 46 andbe discharged from the vapor discharge pipe 22. Due to the mechanicalaction of the blades 28 on the film of liquid on the wall of cylinder18, or to the bursting of vapor bubbles formed in the liquid, finedroplets of liquid will become entrained in the rising vapor stream.Since these liquid droplets represent loss of product if the desiredproduct is the liquid from the bottom of the processor, or contaminationof product if the desired product is the subsequently condensed vapors,it is important that all entrained liquid droplets be separated from thevapor and returned to the processor wall. This complete separation isobtained by the novel separator assembly 46.

As the vapor and entrained droplets rise through the unit between blades28, they necessarily move in a spiral path, the pitch of the spiraldepending on the vertical velocity of the vapor and the speed of therotor. The circular component of this spiral motion causes centrifugalforces which act more strongly on the dense or large liquid dropletsthan on the light vapors. Droplets are therefore thrown out toward thewall of the unit. Coarse droplets generated low in the unit are quicklythrown back into the film of cylinder 18, before reaching the separator14. Fine droplets, however, do not throw out as easily and may reach theseparator 14.

To pass through the separator 14, it is evident that the vapors areconfronted with the series of bafiie rings 54-60. At each ring, thevapor stream divides, a portion moving inward to pass up through theinside diameter of the ring, the remainder passing upward outside thering. The portion moving inward moves against the centrifugal force andsince the force acts more strongly on the droplets, few of the dropletscan make the sharp S-turn to follow this portion of the vapor. Thisseparation is further aided by the fact that droplets continuing withthe vapor stream outside one bafile ring, for example, 60, will acquireadditional outward velocity from the movement of blades 50, therebyassisting the centrifugal force in driving entrainment outward, andmaking it more diflicult for the droplets to follow the inward movingvapor stream at the next ballle ring.

Some droplets may start to make the turn but fail and collide with theunder side of the rings 54-60. Droplets impinging on the under side ofrotating batile rings 54-60 will coalesce with other droplets to formlarge drops which will then be thrown by centrifugal force to the innersurface of feed distributor cylinder 52.

In passing through the nest of bafiie rings 54-60 in the separatorassembly 14, most of the entrained liquid droplets are thrown out to theinner wall of feed distributor cylinder 52 where they will coalesce as afilm. This liquid film will flow downward, out the lower flared portion53 and be thrown into the wall of cylinder 18 along with the fresh feedliquid. If vapor velocities are very high, this film on the inside ofthe feed distributor cylinder 52 will rise toward the upper baflle ring54 and be discharged through holes 66 back into the feed compartmentwhere it will mix with fresh feed and be redisposed on the wall of thecylinder 18.

It will be obvious that the novel separator disclosed may take variousother shapes adn forms without departing from the true spirit of theinvention. For example, the baflles 54-60 may be constructed so thattheir inner edges are angled slightly downward toward the hub, therebyincreasing the angle the vapor stream must make from that of an S tothat approaching a Z configuration. Various other changes andconfigurations that may be used will be apparent to those skilled in theprocessing art.

It will be apparent from the foregoing that by dividing the spiralvertical flow of the vapor into a number of separate streams by asuccession of baffle rings, the height and diameter of the separatorsection are held to minimum proportions and that each increment of thevapor flow is subjected to an effective centrifugal action to remove amaximum of entrained liquid droplets.

The invention may be embodied in other specific forms Without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. An entertainment separator for a thin film thermal processorcomprising a housing, means for introducing a rising vapor stream intosaid housing, shaft means rotatably mounted in said housing, hub meansmounted so as to rotate with said shaft, a plurality of stepped vanesspaced about the periphery of said hub and extending radially outwardtherefrom, and a plurality of spaced, horizontally disposed, verticallydisplaced and concentrically arranged baflie rings secured to the stepsof said vanes for deflecting said rising vapor stream so as to removeentrained droplets therefrom and vapor outlet means connected to saidhousing downstream from said vanes and battle rings.

2. An entrainment separator as defined in claim 1 wherein each of saidrings except the lowermost has an inside diameter that is the same asthe outside diameter of the next lower ring in said arrangement, saidlowest ring having a diameter larger than the hub means.

3. An entrainment separator as defined in claim 1 wherein each of saidrings except the lowermost has an inside diameter that is less than theoutside diameter of the next lower ring in said arrangement, said lowestring having a diameter larger than the hub means.

4. A thin film processor consisting of an evaporator and separator, saidevaporator comprising a chamber having a substantially verticalcylindrical wall, means for heating said Wall, rotor means rotatablymounted in said chamber substantially coaxially with said wall, aplurality of vanes spaced around the circumference of said rotor andextending radially outward therefrom into close proximity of said wall,means at the upper end of said chamber for securing said separator tosaid evaporator, said separator comprising a chamber having asubstantially vertical cylindrical wall, a shaft rotatably mounted insaid separator chamber and connected to said rotor of said evaporator, aplurality of vanes spaced around the circumference of said shaft andextending radially outward therefrom within the separator chamber, afeed distributor cylinder secured to and surrounding said vanes Withinthe separator chamber, horizontally disposed annuIar baffie meanscarried by said vanes within the separator chamber, a feed compartmentring secured to the interior of said separator chamber just above saidvanes within the separator chamber, thereby forming in part a feedcompartment between said Wall and said cylinder, said feed compartmentcommunicating with said chamber of said evaporator, outlet meansconnected to said separator chamber, means for introducing liquidmaterial to be vaporized into said feed compartment and said evaporator,said shaft and said rotor being rotatable whereby said vapor issubjected to centrifugal force in addition to deflection by said bafflemeans so as to free the vapor from entrained droplets.

5. A centrifugal throw-out separator comprising a chamber havingsubstantially vertical cylindrical walls, shaft means rotatably mountedin said chamber, hub means mounted on said shaft, a plurality of vanesspaced around the circumference of said hub and extending radiallyoutward therefrom, a plurality of vertically spaced, horizontallydisposed baffle rings secured to said vanes in stacked assembly, theoutside diameter of a lower ring being approximately equal to the insidediameter of the adjacent upper ring of said stacked assembly, a feeddistributor cylinder having a flared-out lower edge secured to andsurrounding the outer edges of said vanes, a feed compartment ringsecured to the wall of said chamber just above said vanes therebyforming in part a feed compartment between said Walls and said cylinder,inlet liquid feed means connected to said feed compartment, vapor outletmeans located at the top of said chamber, and means for securing anevaporator assembly to the lower portion of said chamber whereby fluidmaterial entering said feed compartment will gravitate into saidevaporator assembly from said feed distributor cylinder, said evaporatorassembly producing a rising vapor stream, and means for passing saidvapor stream through said bafiie rings and rotatable vanes so that saidvapor is subjected to centrifugal force in addition to deflection bysaid bafile means freeing it from entrained droplets.

References (Iited by the Examiner UNITED STATES PATENTS 2,126,481 8/1938Lapp et al 55-408 X 2,166,722 7/1939 Salsas-Serra 26189 X 2,403,0897/1946 Lars 233-32 X 2,807,321 9/1957 Schneider 159-13 2,974,725 3/ 1961Samesreuther et al 1596 FOREIGN PATENTS 579,858 7/1959 Canada. 740,82511/ 1955 Great Britain.

NORMAN YUDKOFF, Primary Examiner.

HERBERT L. MARTIN, Examiner.

1. AN ENTERTAINMENT SEPARATOR FOR A THIN FILM THERMAL PROCESSORCOMPRISING A HOUSING, MEANS FOR INTRODUCING A RISING VAPOR STREAM INTOSAID HOUSING, SHAFT MEANS ROTATABLY MOUNTED IN SAID HOUSING, HUB MEANSMOUNTED SO AS TO ROTATE WITH SAID SHAFT, A PLURALITY OF STEPPED VANESSPACED ABOUT THE PERIPHERY OF SAID HUB AND EXTENDING RADIALLY OUTWARDTHEREFROM, AND A PLURALITY OF SPACED, HORIZONTALLY DISPOSED, VERTICALLYDISPLACED AND CONCENTRICALLY ARRANGED BAFFLE RINGS SECURED TO THE STEPSOF SAID VANES FOR DEFLECTING SAID RISING VAPOR STREAM SO AS TO REMOVEENTRAINED DROPLETS THEREFROM AND VAPOR OUTLET MEANS CONNECTED TO SAIDHOUSING DOWNSTREAM FROM SAID VANES AND BAFFLE RINGS.